<?php
/**
 * Zend Framework
 *
 * LICENSE
 *
 * This source file is subject to the new BSD license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://framework.zend.com/license/new-bsd
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@zend.com so we can send you a copy immediately.
 *
 * @category   Zend
 * @package    Zend_Pdf
 * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 * @version    $Id: Trailer.php 18993 2009-11-15 17:09:16Z alexander $
 */


/**
 * PDF file trailer
 *
 * @package    Zend_Pdf
 * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 */
abstract class Zend_Pdf_Trailer
{
	private static $_allowedKeys = array('Size', 'Prev', 'Root', 'Encrypt', 'Info', 'ID', 'Index', 'W', 'XRefStm', 'DocChecksum');

	/**
	 * Trailer dictionary.
	 *
	 * @var Zend_Pdf_Element_Dictionary
	 */
	private $_dict;

	/**
	 * Check if key is correct
	 *
	 * @param string $key
	 * @throws Zend_Pdf_Exception
	 */
	private function _checkDictKey($key)
	{
		if ( !in_array($key, self::$_allowedKeys) ) {
			/** @todo Make warning (log entry) instead of an exception */
			require_once 'Zend/Pdf/Exception.php';
			throw new Zend_Pdf_Exception("Unknown trailer dictionary key: '$key'.");
		}
	}


	/**
	 * Object constructor
	 *
	 * @param Zend_Pdf_Element_Dictionary $dict
	 */
	public function __construct(Zend_Pdf_Element_Dictionary $dict)
	{
		$this->_dict   = $dict;

		foreach ($this->_dict->getKeys() as $dictKey) {
			$this->_checkDictKey($dictKey);
		}
	}

	/**
	 * Get handler
	 *
	 * @param string $property
	 * @return mixed
	 */
	public function __get($property)
	{
		return $this->_dict->$property;
	}

	/**
	 * Set handler
	 *
	 * @param string $property
	 * @param  mixed $value
	 */
	public function __set($property, $value)
	{
		$this->_checkDictKey($property);
		$this->_dict->$property = $value;
	}

	/**
	 * Return string trailer representation
	 *
	 * @return string
	 */
	public function toString()
	{
		return "trailer\n" . $this->_dict->toString() . "\n";
	}


	/**
	 * Get length of source PDF
	 *
	 * @return string
	 */
	abstract public function getPDFLength();

	/**
	 * Get PDF String
	 *
	 * @return string
	 */
	abstract public function getPDFString();

	/**
	 * Get header of free objects list
	 * Returns object number of last free object
	 *
	 * @return integer
	 */
	abstract public function getLastFreeObject();
}
